diff --git a/artiq/coredevice/ad9154.py b/artiq/coredevice/ad9154.py
index 792c56652..64bb7fbf3 100644
--- a/artiq/coredevice/ad9154.py
+++ b/artiq/coredevice/ad9154.py
@@ -42,6 +42,11 @@ def ad9154_jesd_prbs(prbs: TInt32) -> TNone:
     raise NotImplementedError("syscall not simulated")
 
 
+@syscall(flags={"nounwind", "nowrite"})
+def ad9154_jesd_stpl(prbs: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
 class AD9154:
     """AD9154-FMC-EBZ SPI support
 
@@ -95,3 +100,7 @@ class AD9154:
     @kernel
     def jesd_prbs(self, prbs):
         ad9154_jesd_prbs(prbs)
+
+    @kernel
+    def jesd_stpl(self, enable):
+        ad9154_jesd_stpl(enable)
diff --git a/artiq/gateware/targets/kc705.py b/artiq/gateware/targets/kc705.py
index 82a459f87..749cc6c20 100755
--- a/artiq/gateware/targets/kc705.py
+++ b/artiq/gateware/targets/kc705.py
@@ -544,15 +544,6 @@ class Phaser(_NIST_Ions):
             # while at 5 GBps, take every second sample... FIXME
             self.comb += conv.eq(Cat(ch.o[::2]))
 
-        if False:
-            # short transport layer test pattern
-            self.comb += [
-                self.ad9154.jesd_core.transport.sink.converter0.eq(0x01230123),
-                self.ad9154.jesd_core.transport.sink.converter1.eq(0x45674567),
-                self.ad9154.jesd_core.transport.sink.converter2.eq(0x89ab89ab),
-                self.ad9154.jesd_core.transport.sink.converter3.eq(0xcdefcdef)
-            ]
-
         self.comb += jesd_sync.eq(self.ad9154.jesd_sync)
 
 
diff --git a/artiq/runtime/ad9154.c b/artiq/runtime/ad9154.c
index 0711af8dc..31704bc3d 100644
--- a/artiq/runtime/ad9154.c
+++ b/artiq/runtime/ad9154.c
@@ -69,4 +69,9 @@ void ad9154_jesd_prbs(int p)
     ad9154_jesd_control_prbs_config_write(p);
 }
 
+void ad9154_jesd_stpl(int en)
+{
+    ad9154_jesd_control_stpl_enable_write(en);
+}
+
 #endif /* CONFIG_AD9154_DAC_CS */
diff --git a/artiq/runtime/ad9154.h b/artiq/runtime/ad9154.h
index 9ea6d0e5d..d6fa93d85 100644
--- a/artiq/runtime/ad9154.h
+++ b/artiq/runtime/ad9154.h
@@ -13,6 +13,7 @@ uint8_t ad9516_read(uint16_t addr);
 void ad9154_jesd_enable(int en);
 int ad9154_jesd_ready(void);
 void ad9154_jesd_prbs(int p);
+void ad9154_jesd_stpl(int en);
 
 #endif
 #endif
diff --git a/artiq/runtime/ksupport.c b/artiq/runtime/ksupport.c
index fb3f6dff5..4bc8abec8 100644
--- a/artiq/runtime/ksupport.c
+++ b/artiq/runtime/ksupport.c
@@ -147,6 +147,7 @@ static const struct symbol runtime_exports[] = {
     {"ad9154_jesd_enable", &ad9154_jesd_enable},
     {"ad9154_jesd_ready", &ad9154_jesd_ready},
     {"ad9154_jesd_prbs", &ad9154_jesd_prbs},
+    {"ad9154_jesd_stpl", &ad9154_jesd_stpl},
 #endif
 
     /* end */